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Cubic feet and yards of lava rock for landscape beds or a gas fire pit, with bag counts.
With these inputs:
| Result | Value |
|---|---|
| Lava rock | 2.4 cu ft |
| 10 lb bags (≈0.25 cu ft) | 10 bags |
| Weight | 94 lb |
| Cost | $120 – $250 |
| Area | 7.07 sq ft (36" diameter) |
| Depth | 4 in |
| Volume | 2.4 cu ft · 0.09 yd³ |
| Weight (≈40 lb per cu ft) | 94 lb |
Cover the burner with 1 to 2 inches of lava rock and no more — deeper rock chokes the flame and can trap gas. Use rock rated for fire features, rinsed and fully dried before the first burn.
Lava rock is so light — about half the weight of ordinary gravel — that tonnage-based gravel calculators overestimate what you need to buy. This lava rock calculator works in volume: cubic feet and yards for a landscape bed, or the fill for a gas fire pit or fire table burner pan.
Measure the burner pan: a 36 inch round pan filled 4 inches deep needs about 2.4 cubic feet of lava rock — roughly 94 lb, or ten 10 lb bags. Keep 1 to 2 inches of rock over the burner itself.
About 1,000 to 1,200 pounds, roughly half the weight of ordinary gravel. That is why lava rock is sold by volume, and why a gravel calculator that works in tons will overestimate it.
A cubic yard covers 162 square feet at 2 inches deep, 108 square feet at 3 inches, or 81 square feet at 4 inches — the same as any other material, because coverage depends on volume, not weight.
It is light, cheap to haul, holds its colour, and does not decompose. On the downside it can hold heat against plants in full sun and is sharp to handle. It works best in dry beds, around succulents, and as a mulch substitute in low-water gardens.
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